The present invention relates to a surfactant composition comprising an alkyl amine ethoxylate for use in an aqueous liquid. Such an aqueous liquid can be a drilling fluid or a fluid used to stimulate oil production from a subterranean reservoir. The alkyl group of the alkyl amine ethoxylate contains suitably between 10 and 20 carbon atoms and more suitable between 16 and 18 carbon atoms; the number of ethylene oxide groups is suitably between 3 and 15 and more suitably between 10 and 15.
At ambient temperature alkyl amine ethoxylate is a viscous waxlike liquid, which if mixed with water at ambient temperature and at a concentration between about 15 percent by mass and 80 percent by mass forms a gel. Therefore when a volume of alkyl amine ethoxylate is mixed with water a gel is formed on the outer surface of the volume, so that the volume is covered with a skin through which water can pass slowly. In order to dissolve the volume of alkyl amine ethoxylate the mixture has to be stirred to break the volume in smaller parts. Complete dissolution will only occur when the alkyl amine ethoxylate concentration is below about 15 percent by mass.